The present invention relates to quality control.
In particular, the present invention relates to material monitoring apparatus for determining the quality of a sheet material being manufactured.
In various manufacturing industries, such as in the manufacture of paper and paperboard, there is a need for determining the quality of the material being produced. Thus, in the manufacture of paper there is generally a need to know the dirt content of a running web, as well as the number of flaws and the fiber distribution in the web. The monitoring of the paper quality not only determines the value of the finished paper material, but also provides an indication of the effectiveness of the manufacturing equipment and the filtering system being used, as well as providing an indication of the quality of the original stock material. At the present time, quality control of the manufactured paper is generally accomplished using off-line, laboratory methods. Samples of the finished product are selected and using laboratory equipment, the amount of dirt content as well as other defects are measured and catalogued.
While such off-line laboratory methods may provide accurate results, the time required for completing analysis is often excessive and provides too great a delay for immediate corrective action. For example, by the time a particular sample of paper is checked for its quality, that batch of paper will have been passed from the machine, and may very well be already packed for shipment to a distributor. Thus, it will often be too late to remove the batch of paper and use it for other purposes. Furthermore, should a particular batch of paper indicate that the original stock is of a poor quality, it would be advisable to change the original stock. However, the excessive delay resulting from the effective testing may make it too late to change the stock and the poor quality stock will be used up before there is any chance to change it. Additionally, the problem causing a poor quality paper may result from poor filtering operation within the manufacturing process. This might easily be corrected if the problem could be detected within s reasonable time. Accordingly, it would be beneficial to provide on-line monitoring of the material to provide an indication of the quality of the paper being produced during the course of the manufacturing process.